package com.example.bbs.util;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class ImageCode {

    public static BufferedImage getBufferedImage(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {
        //设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        //在内存中创建图象
        int width = 80, height = 25;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //获取图形上下文
        Graphics g = image.getGraphics();
        //生成随机类
        Random random = new Random();
        //设定背景色
        g.setColor(getRandColor(220, 250));
        g.fillRect(0, 0, width, height);
        //设定字体
        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
        //画边框
        //g.drawRect(0,0,width-1,height-1);
        g.draw3DRect(0,0,width-1,height-1,true);
        //随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
        g.setColor(getRandColor(160, 200));
        for (int i = 0; i < 155; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int xl = random.nextInt(12);
            int yl = random.nextInt(12);
            g.drawLine(x, y, x + xl, y + yl);
        }
        // 取随机产生的认证码(6位数字)
        String sRand = "";
        String s = "012345678901234567890123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789abcdefghijklmnopqrstuvwxyz";
        for (int i = 0; i < 4; i++) {
            char rand =s.charAt(random.nextInt(s.length()));
            sRand += rand;
            // 将认证码显示到图象中
            g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
            //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
            g.drawString(String.valueOf(rand), 13 * i + 6, 16);
        }
        g.drawOval(0,12,60,11);
        // 将认证码存入SESSION
        request.getSession().setAttribute("rand", sRand.toLowerCase());
        // 图象生效
        g.dispose();
        return image;
    }


    /**
     * 生成随机颜色
     */
    private static Color getRandColor(int fc, int bc) {
        Random random = new Random();
        if (fc > 255)
            fc = 255;
        if (bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

}
